Add hooks for session start and session end

These hooks can be used in loadable modules. A simple test module is
included.

Discussion:  https://postgr.es/m/20170720204733.40f2b7eb.nagata@sraoss.co.jp

Fabrízio de Royes Mello  and Yugo Nagata
Reviewed by Michael Paquier and Aleksandr Parfenov

diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 05c5c194ec6bd26edce607e215ab3eb6ca531c01..d3156ad49efd236e748410c767fb517dfc865de8 100644 (file)
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -169,6 +169,9 @@ static ProcSignalReason RecoveryConflictReason;
 static MemoryContext row_description_context = NULL;
 static StringInfoData row_description_buf;
 
+/* Hook for plugins to get control at start of session */
+session_start_hook_type session_start_hook = NULL;
+
 /* ----------------------------------------------------------------
  *             decls for routines only used in this file
  * ----------------------------------------------------------------
@@ -3857,6 +3860,9 @@ PostgresMain(int argc, char *argv[],
        if (!IsUnderPostmaster)
                PgStartTime = GetCurrentTimestamp();
 
+       if (session_start_hook)
+               (*session_start_hook) ();
+
        /*
         * POSTGRES main processing loop begins here
         *

diff --git a/src/backend/utils/init/postinit.c b/src/backend/utils/init/postinit.c
index 20f1d279e9c0bc3764bcab762869d37c695971c5..16ec376b22173445fe82526f0f1b47826371e919 100644 (file)
--- a/src/backend/utils/init/postinit.c
+++ b/src/backend/utils/init/postinit.c
@@ -76,6 +76,8 @@ static bool ThereIsAtLeastOneRole(void);
 static void process_startup_options(Port *port, bool am_superuser);
 static void process_settings(Oid databaseid, Oid roleid);
 
+/* Hook for plugins to get control at end of session */
+session_end_hook_type session_end_hook = NULL;
 
 /*** InitPostgres support ***/
 
@@ -1154,6 +1156,10 @@ ShutdownPostgres(int code, Datum arg)
         * them explicitly.
         */
        LockReleaseAll(USER_LOCKMETHOD, true);
+
+       /* Hook at session end */
+       if (session_end_hook)
+               (*session_end_hook) ();
 }
 
 

diff --git a/src/include/tcop/tcopprot.h b/src/include/tcop/tcopprot.h
index f8c535c91e34c2a10aeff5eeb7788cb3b05deeaf..9f05bfb4ab56d687e44ecd853c45dfa159917952 100644 (file)
--- a/src/include/tcop/tcopprot.h
+++ b/src/include/tcop/tcopprot.h
@@ -35,6 +35,13 @@ extern PGDLLIMPORT const char *debug_query_string;
 extern int     max_stack_depth;
 extern int     PostAuthDelay;
 
+/* Hook for plugins to get control at start and end of session */
+typedef void (*session_start_hook_type) (void);
+typedef void (*session_end_hook_type) (void);
+
+extern PGDLLIMPORT session_start_hook_type session_start_hook;
+extern PGDLLIMPORT session_end_hook_type session_end_hook;
+
 /* GUC-configurable parameters */
 
 typedef enum

diff --git a/src/test/modules/Makefile b/src/test/modules/Makefile
index b7ed0af021f6306741428aadef69d455d9d7601a..7246552d3860feee4936d80bac0a2d9c3ac6773d 100644 (file)
--- a/src/test/modules/Makefile
+++ b/src/test/modules/Makefile
@@ -15,6 +15,7 @@ SUBDIRS = \
                  test_pg_dump \
                  test_rbtree \
                  test_rls_hooks \
+                 test_session_hooks \
                  test_shm_mq \
                  worker_spi
 

diff --git a/src/test/modules/test_session_hooks/.gitignore b/src/test/modules/test_session_hooks/.gitignore
new file mode 100644 (file)
index 0000000..5dcb3ff
--- /dev/null
+++ b/src/test/modules/test_session_hooks/.gitignore
@@ -0,0 +1,4 @@
+# Generated subdirectories
+/log/
+/results/
+/tmp_check/

diff --git a/src/test/modules/test_session_hooks/Makefile b/src/test/modules/test_session_hooks/Makefile
new file mode 100644 (file)
index 0000000..c5c3860
--- /dev/null
+++ b/src/test/modules/test_session_hooks/Makefile
@@ -0,0 +1,21 @@
+# src/test/modules/test_session_hooks/Makefile
+
+MODULES = test_session_hooks
+PGFILEDESC = "test_session_hooks - Test session hooks with an extension"
+
+EXTENSION = test_session_hooks
+DATA = test_session_hooks--1.0.sql
+
+REGRESS = test_session_hooks
+REGRESS_OPTS = --temp-config=$(top_srcdir)/src/test/modules/test_session_hooks/session_hooks.conf
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = src/test/modules/test_session_hooks
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif

diff --git a/src/test/modules/test_session_hooks/README b/src/test/modules/test_session_hooks/README
new file mode 100644 (file)
index 0000000..9cb4202
--- /dev/null
+++ b/src/test/modules/test_session_hooks/README
@@ -0,0 +1,2 @@
+test_session_hooks is an example of how to use session start and end
+hooks.

diff --git a/src/test/modules/test_session_hooks/expected/test_session_hooks.out b/src/test/modules/test_session_hooks/expected/test_session_hooks.out
new file mode 100644 (file)
index 0000000..be1b949
--- /dev/null
+++ b/src/test/modules/test_session_hooks/expected/test_session_hooks.out
@@ -0,0 +1,31 @@
+CREATE ROLE regress_sess_hook_usr1 SUPERUSER LOGIN;
+CREATE ROLE regress_sess_hook_usr2 SUPERUSER LOGIN;
+\set prevdb :DBNAME
+\set prevusr :USER
+CREATE TABLE session_hook_log(id SERIAL, dbname TEXT, username TEXT, hook_at TEXT);
+SELECT * FROM session_hook_log ORDER BY id;
+ id | dbname | username | hook_at 
+----+--------+----------+---------
+(0 rows)
+
+\c :prevdb regress_sess_hook_usr1
+SELECT * FROM session_hook_log ORDER BY id;
+ id | dbname | username | hook_at 
+----+--------+----------+---------
+(0 rows)
+
+\c :prevdb regress_sess_hook_usr2
+SELECT * FROM session_hook_log ORDER BY id;
+ id |       dbname       |        username        | hook_at 
+----+--------------------+------------------------+---------
+  1 | contrib_regression | regress_sess_hook_usr2 | START
+(1 row)
+
+\c :prevdb :prevusr
+SELECT * FROM session_hook_log ORDER BY id;
+ id |       dbname       |        username        | hook_at 
+----+--------------------+------------------------+---------
+  1 | contrib_regression | regress_sess_hook_usr2 | START
+  2 | contrib_regression | regress_sess_hook_usr2 | END
+(2 rows)
+

diff --git a/src/test/modules/test_session_hooks/session_hooks.conf b/src/test/modules/test_session_hooks/session_hooks.conf
new file mode 100644 (file)
index 0000000..fc62b4a
--- /dev/null
+++ b/src/test/modules/test_session_hooks/session_hooks.conf
@@ -0,0 +1,2 @@
+shared_preload_libraries = 'test_session_hooks'
+test_session_hooks.username = regress_sess_hook_usr2

diff --git a/src/test/modules/test_session_hooks/sql/test_session_hooks.sql b/src/test/modules/test_session_hooks/sql/test_session_hooks.sql
new file mode 100644 (file)
index 0000000..5e08647
--- /dev/null
+++ b/src/test/modules/test_session_hooks/sql/test_session_hooks.sql
@@ -0,0 +1,12 @@
+CREATE ROLE regress_sess_hook_usr1 SUPERUSER LOGIN;
+CREATE ROLE regress_sess_hook_usr2 SUPERUSER LOGIN;
+\set prevdb :DBNAME
+\set prevusr :USER
+CREATE TABLE session_hook_log(id SERIAL, dbname TEXT, username TEXT, hook_at TEXT);
+SELECT * FROM session_hook_log ORDER BY id;
+\c :prevdb regress_sess_hook_usr1
+SELECT * FROM session_hook_log ORDER BY id;
+\c :prevdb regress_sess_hook_usr2
+SELECT * FROM session_hook_log ORDER BY id;
+\c :prevdb :prevusr
+SELECT * FROM session_hook_log ORDER BY id;

diff --git a/src/test/modules/test_session_hooks/test_session_hooks--1.0.sql b/src/test/modules/test_session_hooks/test_session_hooks--1.0.sql
new file mode 100644 (file)
index 0000000..16bcee9
--- /dev/null
+++ b/src/test/modules/test_session_hooks/test_session_hooks--1.0.sql
@@ -0,0 +1,4 @@
+/* src/test/modules/test_hook_session/test_hook_session--1.0.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "CREATE EXTENSION test_hook_session" to load this file. \quit

diff --git a/src/test/modules/test_session_hooks/test_session_hooks.c b/src/test/modules/test_session_hooks/test_session_hooks.c
new file mode 100644 (file)
index 0000000..4e2eef1
--- /dev/null
+++ b/src/test/modules/test_session_hooks/test_session_hooks.c
@@ -0,0 +1,134 @@
+/* -------------------------------------------------------------------------
+ *
+ * test_session_hooks.c
+ *             Code for testing SESSION hooks.
+ *
+ * Copyright (c) 2010-2017, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *             src/test/modules/test_session_hooks/test_session_hooks.c
+ *
+ * -------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/xact.h"
+#include "commands/dbcommands.h"
+#include "executor/spi.h"
+#include "lib/stringinfo.h"
+#include "miscadmin.h"
+#include "tcop/tcopprot.h"
+#include "utils/snapmgr.h"
+#include "utils/builtins.h"
+
+PG_MODULE_MAGIC;
+
+/* Entry point of library loading/unloading */
+void           _PG_init(void);
+void           _PG_fini(void);
+
+/* GUC variables */
+static char *session_hook_username = "postgres";
+
+/* Original Hook */
+static session_start_hook_type prev_session_start_hook = NULL;
+static session_end_hook_type prev_session_end_hook = NULL;
+
+static void
+register_session_hook(const char *hook_at)
+{
+       const char *username;
+
+       StartTransactionCommand();
+       SPI_connect();
+       PushActiveSnapshot(GetTransactionSnapshot());
+
+       username = GetUserNameFromId(GetUserId(), false);
+
+       /* Register log just for configured username */
+       if (!strcmp(username, session_hook_username))
+       {
+               const char *dbname;
+               int ret;
+               StringInfoData  buf;
+
+               dbname = get_database_name(MyDatabaseId);
+
+               initStringInfo(&buf);
+
+               appendStringInfo(&buf, "INSERT INTO session_hook_log (dbname, username, hook_at) ");
+               appendStringInfo(&buf, "VALUES ('%s', '%s', '%s');",
+                       dbname, username, hook_at);
+
+               ret = SPI_exec(buf.data, 0);
+               if (ret != SPI_OK_INSERT)
+                       elog(ERROR, "SPI_execute failed: error code %d", ret);
+       }
+
+       SPI_finish();
+       PopActiveSnapshot();
+       CommitTransactionCommand();
+}
+
+/* sample session start hook function */
+static void
+sample_session_start_hook()
+{
+       /* Hook just normal backends */
+       if (MyBackendId != InvalidBackendId)
+       {
+               (void) register_session_hook("START");
+
+               if (prev_session_start_hook)
+                       prev_session_start_hook();
+       }
+}
+
+/* sample session end hook function */
+static void
+sample_session_end_hook()
+{
+       /* Hook just normal backends */
+       if (MyBackendId != InvalidBackendId)
+       {
+               if (prev_session_end_hook)
+                       prev_session_end_hook();
+
+               (void) register_session_hook("END");
+       }
+}
+
+/*
+ * Module Load Callback
+ */
+void
+_PG_init(void)
+{
+       /* Save Hooks for Unload */
+       prev_session_start_hook = session_start_hook;
+       prev_session_end_hook = session_end_hook;
+
+       /* Set New Hooks */
+       session_start_hook = sample_session_start_hook;
+       session_end_hook = sample_session_end_hook;
+
+       /* Load GUCs */
+       DefineCustomStringVariable("test_session_hooks.username",
+                                                          "Username to register log on session start or end",
+                                                          NULL,
+                                                          &session_hook_username,
+                                                          "postgres",
+                                                          PGC_SIGHUP,
+                                                          0, NULL, NULL, NULL);
+}
+
+/*
+ * Module Unload Callback
+ */
+void
+_PG_fini(void)
+{
+       /* Uninstall Hooks */
+       session_start_hook = prev_session_start_hook;
+       session_end_hook = prev_session_end_hook;
+}

diff --git a/src/test/modules/test_session_hooks/test_session_hooks.control b/src/test/modules/test_session_hooks/test_session_hooks.control
new file mode 100644 (file)
index 0000000..7d7ef9f
--- /dev/null
+++ b/src/test/modules/test_session_hooks/test_session_hooks.control
@@ -0,0 +1,3 @@
+comment = 'Test start/end hook session with an extension'
+default_version = '1.0'
+relocatable = true